This tissue culture facility has been in operation since 1973, functioning as a centralized core laboratory to provide research material to the projects of the medical oncology research program. Stock cell lines used in the various projects are maintained by the laboratory. Cell line profiles and a frozen cell inventory are also maintained. The Core has the capacity to prepare relatively large volumes of tissue culture cells for individual studies. It also may perform routine cell experiments, e.g. preparation of cell pellets after exposure of cells to different drugs or hormonal manipulations, as well as growth assays (counts or MTT assays for anchorage-dependent growth, soft agar for anchorage-independent growth). Preparation and maintenance of transfectants are also important activities of this Core. Centralization of this fully equipped laboratory operation provides: (a) optimum efficiency in management and use of time, equipment, resources and physical facilities; (b) Coordination of preparation and ordering of tissue culture supplies, with improved quality assurance of reagents; (c) Extensive inventory, continuous source, and quality control of breast tumor and other pertinent cell lines; and (d) A service for the production of tumor-bearing animals. This centralization reduces overall costs of supplies and effort required for routine maintenance and quality control of cell cultures for all Program Project investigators.